One more note on "tools"....I forgot this one:

Do you recognize it? Can you name it?  No, it's not modern art (although I'm wondering what it would look like pixelated).

Carpet padding!  I'm so glad I held back a piece of the old padding for my old knees.   Crawling around on a concrete floor takes it's toll, and this has helped so much. 

Take care of your knees...keep some padding around!